1. Field of the Invention
The present invention relates to an apparatus for incinerating waste materials such as waste tires, for example.
2. Description of the Prior Art
One known apparatus for incinerating waste materials such as waste tires is disclosed in Japanese Laid-Open Patent Publication No. 2-135280. Specifically, the disclosed incinerating apparatus comprises an apparatus for incinerating a waste material by processing the waste material through dry distillation and gasification.
The disclosed incinerating apparatus has a gasification furnace in which a waste material is placed. In the gasification furnace, a portion of the waste material is burned while the remainder of the waste material is subjected to a dry distillation (i.e., thermally decomposed) with the heat of combustion, until finally the waste material is completely combusted and ashed. A combustible gas produced when the waste material is thermally decomposed is introduced from a gasification furnace through a gas passage into a combustion furnace. In the combustion furnace, the supplied combustible gas is mixed with oxygen (air) and burned at such a temperature as to sufficiently reduce nitrogen oxides. In this manner, the waste material is combusted without causing environmental pollutions which would otherwise result from excessive nitrogen oxides.
More specifically, combustion of a portion of the waste material and dry distillation of the remainder of the waste material in the gasification furnace, and combustion of the combustible gas in the combustion furnace are carried out as follows:
The combustion of a portion of the waste material and dry distillation of the remainder of the waste material are started by placing the waste material in the gasification furnace and thereafter supplying combustion flames from an ignition nozzle of an igniter mounted in a lower side wall of the gasification furnace to the waste material for a predetermined period of time. When the combustion flames are supplied, a portion of the waste material near the ignition nozzle is ignited and the fire is transferred between pieces of the waste material. The combustion spreads to surrounding pieces of the waste material and becomes stable. When the stable combustion of the portion of the waste material is started, dry distillation of the waste material is started by the heat of combustion, generating a combustible gas. The amount of the generated combustible gas increases as the dry distillation of the waste material progresses.
The combustible gas generated by the dry distillation in the gasification furnace is introduced through the gas passage into the combustion furnace. In the combustion furnace, the combustible gas is mixed with oxygen and ignited by an igniter mounted in the combustion furnace. At this time, the temperature of the combustible gas as it is burned in the combustion furnace is detected by a temperature sensor mounted in the combustion furnace. After the waste material has been ignited, the detected temperature increases as the amount of the combustible gas generated in the gasification furnace increases and hence the combustible gas introduced into the combustion furnace increases.
When the detected temperature of the combustible gas as it is burned increases until it reaches a temperature at which the combustible gas starts spontaneous combustion, the igniter in the combustion furnace is inactivated, and an oxygen supply connected to the gasification furnace regulates the amount of oxygen supplied to the gasification furnace such that the detected temperature will be kept at a predetermined substantially constant level at which the amount of nitrogen oxides generated by the combustion of the combustible gas is sufficiently small, and supplies the gasification furnace with an amount of oxygen necessary to effect combustion of the portion of the waste material and dry distillation of the remainder of the waste material.
The temperature at which the combustible gas is burned in the combustion furnace is therefore maintained at a substantially constant level at which the amount of nitrogen oxides is sufficiently small. The combustible gas is therefore completely combusted without the danger of environmental pollutions.
To ignite a portion of the waste material placed in the gasification furnace, combustion flames are supplied from the ignition nozzle to the waste material for a predetermined period of time, as described above. When the combustion of the portion of the waste material is stabilized, stable dry distillation progresses with the heat of combustion until the waste material is ashed. It is preferable that the overall process from the ignition of the portion of the waste material to the ashing of the waste material be effected automatically for increased incinerating efficiency and reduced labor cost.
If a different type of waste material is placed in a different manner in the gasification furnace, then when combustion flames are supplied from the ignition nozzle to the waste material, the fire may not be well transferred between pieces of the waste material, and the combustion may not spread. In this case, the combustion of the waste material becomes unstable and suffers a flame failure, and the dry distillation is stopped. It has heretofore been customary for the operator to confirm whether the waste material is ignited in a manner to keep dry distillation of the waste material in progress, and in the event of an ignition failure, to manually operate the igniter again to re-ignite the waste material. Consequently, the overall process from the ignition of the portion of the waste material to the ashing of the waste material has not been automatized.
It has also been the practice to confirm an ignition of the waste material by detecting a preset temperature as an ignited temperature with a temperature sensor mounted in the gasification furnace. However, since the temperature sensor only confirms an ignition of the waste material automatically, the operator is still required to manually actuate the igniter again in the event of an ignition failure. Depending on the type of the waste material placed in the gasification furnace and the manner in which the waste material is placed in the gasification furnace, the temperature in the gasification furnace may sometimes sharply increase temporarily regardless of the fact that the waste material has not been ignited in a manner to keep dry distillation of the waste material in progress. When the sharply increased temperature is detected by the temperature sensor, an ignition cannot be confirmed reliably.